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MAXIMUM EQUIVALENT VENT LENGTH - - FT. (M) (CONTINUED)
NOTE: Maximum Equivalent Vent Length (MEVL) includes standard and concentric vent termination and does NOT include elbows.
Use Table 2 - Deductions from Maximum Equivalent Vent Length to determine allowable vent length for each application.
Altitude
Unit Size
5
FT (M)
40,000
60,000
4501 to 5000
80,000
(1370 to 1524)
100,000
120,000
140,000
40,000
60,000
80,000
5001 to 6000
100,000
(1524 to 1829)
120,000
140,000
40,000
60,000
80,000
6001 to 7000
100,000
(1829 to 2134)
120,000
140,000
40,000
60,000
80,000
7001 to 8000
100,000
(2134 to 2438)
120,000
140,000
40,000
60,000
80,000
8001 to 9000
100,000
(2438 to 2743)
120,000
140,000
40,000
60,000
80,000
9001 to 10,000
100,000
(2743 to 3048)
120,000
140,000
NOTES:
1. Use only the vent pipe sizes shown for each furnace. It is NOT necessary to choose the smallest diameter pipe possible for venting.
2. NA --- Not allowed. Pressure switch will not close, or flame disturbance may result.
3. Total equivalent vent lengths under 10' for 40,000 BTUH furnaces from 0 to 2000 ft. (0 to 610 M) above sea level require use of an outlet choke plate .
Failure to use an outlet choke when required may result in flame disturbance or flame sense lockout.
4. Not all furnace families include 140,000 BTUH input models.
5. Vent sizing for Canadian installations over 4500 ft (1370 M) above sea level are subject to acceptance by local authorities having jurisdiction.
6. Size both the combustion air and vent pipe independently, then use the larger size for both pipes.
7. Assume the two 45_ elbows equal one 90_ elbow. Wide radius elbows are desirable and may be required in some cases.
8. Elbow and pipe sections within the furnace casing and at the vent termination should not be included in vent length or elbow count.
9. The minimum pipe length is 5 ft. (1.5 M) linear feet (meters) for all applications.
10. Use 3 ---in. (76 mm) diameter vent termination kit for installations requiring 4 ---in. (102 mm) diameter pipe.
Table 3 – Maximum Equivalent Vent Length - - Ft. (M)
4501 to 10,000 Ft. (0 to 1370 M) Altitude
1-1/2
33
(10.1)
171
20
(6.1)
111
13
(4.0)
54
NA
16
NA
NA
4
NA
NA
27
(8.2)
158
16
(4.9)
103
11
(3.4)
49
NA
12
NA
NA
4
NA
NA
21
(6.4)
145
13
(4.0)
96
NA
44
NA
10
NA
NA
4
NA
NA
15
(4.6)
133
10
(3.0)
89
NA
40
NA
NA
NA
NA
4
NA
NA
10
(3.0)
121
7
(2.1)
82
NA
35
NA
NA
NA
NA
4
NA
NA
5
(1.5)
110
NA
76
NA
31
NA
NA
NA
NA
4
NA
NA
DIRECT VENT (2-PIPE) AND SINGLE-PIPE
Vent Pipe Diameter (in.)
2
2-1/2
(52.1)
196
(59.7)
(33.8)
198
(60.4)
(16.5)
146
(44.5)
(4.9)
91
(27.7)
NA
NA
(48.2)
179
(54.6)
(31.4)
186
(56.7)
(14.9)
137
(41.8)
(3.7)
85
(25.9)
NA
NA
(44.2)
162
(49.4)
(29.3)
174
(53.0)
(13.4)
120
(36.6)
(3.0)
79
(24.1)
NA
NA
(40.5)
146
(44.5)
(27.1)
163
(49.7)
(12.2)
120
(36.6)
73
(22.3)
NA
NA
(36.9)
130
(39.6)
(25.0)
152
(46.3)
(10.7)
111
(33.8)
67
(20.4)
NA
NA
(33.5)
115
(35.1)
(23.2)
142
(43.3)
(9.4)
103
(31.4)
62
(18.9)
NA
NA
9
1
3
4
2
NA
NA
221
(67.4)
NA
195
(59.4)
216
200
(61.0)
222
80
(24.4)
211
60
(18.3)
134
NA
NA
207
(63.1)
NA
183
(55.8)
200
188
(57.3)
208
74
(22.6)
199
50
(15.2)
109
NA
NA
194
(59.1)
NA
171
(52.1)
185
178
(54.3)
195
68
(20.7)
187
41
(12.5)
87
NA
NA
181
(55.2)
NA
159
(48.5)
170
167
(50.9)
182
62
(18.9)
175
32
(9.8)
63
NA
NA
168
(51.2)
NA
148
(45.1)
156
157
(47.9)
170
56
(17.1)
164
23
(7.0)
42
NA
NA
156
(47.5)
NA
137
(41.8)
142
147
(44.8)
157
51
(15.5)
153
16
(4.9)
20
(65.8)
(67.7)
(64.3)
(40.8)
(61.0)
(63.4)
(60.7)
(33.2)
(56.4)
(59.4)
(57.0)
(26.5)
(51.8)
(55.5)
(53.3)
(19.2)
(47.5)
(51.8)
(50.0)
(12.8)
(43.3)
(47.9)
(46.6)
(6.1)
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